This invention relates to compositions, methods and apparatus for lubrication of mammalian joints, both natural and artificial.
Synovial fluid acts to lubricate the bearing surfaces of bones and bone-like structures which are held in frictional contact within joints. Synovial fluid lubricates tendons, cartilage, bones, ligaments, and other biological structures that move within the body relative to each other. The human knee is an example of a joint that uses synovial fluid advantageously to provide for lubrication and for friction reduction. Synovial fluid is naturally excreted into the cavity of the joint in a normal healthy knee.
There are publications disclosing the use of propylene glycol and phospholipids in synovial fluid. For example, PCT publication WO 97/22345 to Hills et al. provides a discussion of a method of lubrication of synovial fluid by administering a composition comprising a mixture of phospholipids and propylene glycol. Another publication, PCT publication 89/01777 discloses using hyaluronic acid in saline solution as a lubricant for joints. Hyaluronic acid compositions may reduce the coefficient of kinetic friction between surfaces in contact with each other, and in particular, load bearing surfaces. Another publication, EP 0 767 212A1, is directed to a process for producing an aqueous solution of phosphorycholine group bearing polymer. This publication is directed to producing such compositions as starting materials for cosmetics having skin beautifying effects, and as contact lens cleaning agents.
U.S. Pat. No. 5,902,800 to Green et al. describes pharmaceutical compositions containing dextran, and a method for treatment of joint inflammation and pain brought about by arthritis, physical trauma, or infection using such dextran-containing formulations. The method comprises administering a bimodal molecular weight dextran formulation in conjunction with drugs or pharmaceuticals, such as corticocosteroids, anti-inflammatory drugs, and antibiotics to enhance the effect of dextran in relieving pain and inflammation in an inflamed joint.
The present invention may be presented in many different embodiments, and representative embodiments are described herein. The invention is not limited to only those embodiments described, and a person of skill in the art may readily apply the invention in other ways that are apparent from this specification. Numerous examples are provided, but the invention is not intended to be limited to only those examples provided.
The invention generally comprises a biologically compatible lubricant composition useful for; injecting into damaged or diseased joints, filling cavities and spaces in artificial joints, applying to joints in connection with post-surgical procedures, and other applications in which a synovial fluid having good lubricity and biocompatibility is desirable. Treatment of osteo-arthritic joints is one application for compositions of this invention. In other applications, a composition may be injected following a joint injury, as a visco-supplementation. The compositions may be used as lubricants in artificial joints following total joint replacements. Further, the compositions may be used for maintenance of an artificial joint to minimize wear of bearing surfaces in humans or mammals. In some applications, the compositions may be used to investigate or measure the wear performance of artificial joints in vitro in a joint stimulator for research purposes.
The composition generally comprises an effective amount of dextran and a lipid. In one aspect of the invention, the lipid may be selected from the group of lipids comprising: lipopolysaccharides, sphingolipids, glycolipids, phosphatidyl cholines, phosphatidyl ethanolamines, sphingomyelins, phosphatidyl inositols, phosphatidyl serines, phosphatidylethanolamine, phosphatidylserine, phosphatidylglycerol, phosphatidylinositol, sphingomyelin, dipalmitoyl phosphatidylcholine (DPPC), and phosphatidyl cholines.
In one embodiment of the invention, the composition is presented which has a rheology of the fluid between about 1 and 20 Pa (sec) at a temperature range of about 25-45 C. The dextran typically comprises less than 40% by weight of the solution, and more preferably about 20% by weight, and still more preferably about 10% by weight or less.
In another aspect of the invention, a synthetic synovial fluid is disclosed comprising dextran and a phospholipid. In many instances the fluid comprises a crosslinked hydrogel. Many different phospholipids work well in this composition, and one desirable phospholipid is dipalmitoyl phosphatidylcholine (DPPC), which is further discussed in connection with the Example below.
A method of lubricating a joint or other physiological articulation is also presented by way of this invention. The method generally comprises administering to a joint or articulation in an effective amount of a composition comprising one or more phospholipids and dextran-based hydrogel which acts as a carrier. The method may be applied in instances for which the joint is a natural joint, or an artificial joint. In one application, the method may be applied in which the administration of the composition follows a total joint replacement operation. In one aspect of the invention, the method may include applying the lubricant compositions into an artificial joint simulator to simulate wear performance of the joint.